Question: Why does Lana at the end of the movie call Brandon "Teena"?
Answer: Brandon's birth name is Teena Tenae Brandon. When Teena decided to become a man, he reversed his first and last name to become Brandon Teena. Lana may have continued to call him Teena as a form of "I know the real you" familiarity "pet name".
Question: What is the name of the song playing during the very last scene with Lana driving and who sings it?
Answer: Bluest Eyes in Texas, remade by Sheryl Crow, originally by Little Texas.